Trains are boring places, and always have been, but thanks to the world of mobile gaming long, drawn-out and delayed journeys can be made all the more entertaining with cheap apps that take your mind away from Christopher the sweaty commuter and his rancid armpit and give your brain something to do.

Photon is the very definition of a causal game, and it's great for making train journeys less bothersome. It's absurdly simple to understand and incredibly well explained by the simpe step-by-step instructions. But its appeal and ability to distract are epic.

Photon

The idea is simple: a Tetris-style screen is presented, in to which coloured circles drop. Your job is to draw a line through three of them, and in so doing eliminate them from the board. And, bar a few other challenges along the way, that's it.

Obviously, like Tetris, things get more and more frantic as you go. And if you're feeling skillful, you can earn more points by speeding things up with the level advance button. This means things start turning up in larger numbers, and far quicker too.

In addition to speeding things up, there are also "special" circles, which appear and need to be dispatched quickly, to prevent your screen from becoming too congested. If you have too much on screen, then you'll quickly lose the game. This involves eliminating the usual coloured circles but drawing lines through these special balls at the same time. Some take more than one attempt to destroy, so keep an eye out for those.

We can only really score a game on how it makes time pass, and how much we want to play it when we aren't playing it. Photon, it has to be said, is one of those games that we just can't wait to get back to. We aren't, for example, playing it now, but we'd like to be, rather than writing these words about it.

Certainly, the time we spent going from Clapham Junction to Shepherd's Bush was a lot less tedious, even in the face of massive delays.

We like that Classic mode is free to play too. There's enough here to get you hooked, before you spend the tiny sum of £0.67 buying full access to the Arcade mode. The even better news is that the developer is so certain that you'll be hooked that it allows you 10 free goes in Arcade mode.

And there is a lot more to offer in Arcade. Points can be used to make the game easier. For example, you can lengthen the distance over which you can connect circles together, or reduce the minimum number needed to connect from three to two. These all "cost" but the amounts are virtual and reasonably small. If you buy the game before your free trial expires, you'll also get some bonus credits for free.

Photon is an addictive, fun game. It makes public transport bearable, and for that reason it's well worth downloading. And for £0.67, the full version is a bargain too.